Sensing electrode oxygen control in an oxygen sensor

Abstract

An oxygen sensor comprises a housing defining an interior space, a sensing electrode, a reference electrode, a counter electrode, a separator retaining an electrolyte, and a chamber within the housing. The retained electrolyte provides ionically conductive pathways between each of the sensing electrode, the reference electrode, and the counter electrode within the housing, and the chamber contains the sensing electrode. The chamber comprises an opening, and the separator extends into the chamber and substantially fills the opening.

What is claimed is: 
     
       1. An oxygen sensor comprising:
 a housing defining an interior space; 
 a sensing electrode; 
 a reference electrode; 
 a counter electrode, wherein the sensing electrode, the reference electrode and the counter electrode are disposed in a planar arrangement and wherein the reference electrode is disposed between the sensing electrode and the counter electrode; 
 a separator retaining an electrolyte, wherein the electrolyte provides an ionically conductive pathway between each of the sensing electrode, the reference electrode, and the counter electrode within the housing, wherein a shortest path between the sensing electrode and the counter electrode on the ionically conductive pathway exists through the reference electrode; and 
 a chamber within the housing, wherein the chamber contains the sensing electrode, wherein the chamber comprises an opening, and wherein the separator extends into the chamber and substantially fills the opening so that the rate of oxygen diffusion to the sensing electrode is less than a consumption rate of oxygen at the sensing electrode, wherein the reference electrode and the counter electrode are outside of the chamber. 
 
     
     
       2. The oxygen sensor of  claim 1 , wherein the housing comprises a cap coupled to a body, wherein the chamber is formed by an inner surface of the cap, an inner surface of the body, and a seal disposed between the cap and the body around the sensing electrode. 
     
     
       3. The oxygen sensor of  claim 2 , wherein a layer of the electrolyte is maintained at the seal between the cap and the body. 
     
     
       4. The oxygen sensor of  claim 1 , wherein the sensing electrode, the reference electrode, and the counter electrode are coupled through an external circuit, wherein the external circuit detects a current between the sensing electrode and the counter electrode to determine a concentration of oxygen in an ambient gas. 
     
     
       5. The oxygen sensor of  claim 1 , wherein a portion of the separator is contained within the chamber, and where a length of a portion of the electrolyte in the separator within the chamber is configured to provide an oxygen concentration at the sensing electrode in a range between zero and 1%. 
     
     
       6. The oxygen sensor of  claim 1 , wherein a ratio of a distance between the counter electrode and the reference electrode on the ionically conductive pathway to a distance between the counter electrode and the sensing electrode on the ionically conductive pathway is between about 1:1 to about 1:10. 
     
     
       7. The oxygen sensor of  claim 1 , wherein a distance between the counter electrode and the reference electrode on the ionically conductive pathway is between about 1 mm to about 20 mm, and wherein a distance between the sensing electrode and the counter electrode on the ionically conductive pathway is between about 5 mm to about 30 mm. 
     
     
       8. The oxygen sensor of  claim 1 , wherein a length and cross-section area of the separator are configured to provide a lower diffusional flowrate of oxygen through the electrolyte to the sensing electrode than a reduction rate of oxygen at the sensing electrode. 
     
     
       9. The oxygen sensor of  claim 1 , wherein the separator extends into the chamber into contact with the sensing electrode, and wherein the separator substantially fills the opening into the chamber so that the rate of oxygen diffusion to the sensing electrode is less than a consumption rate of oxygen at the sensing electrode. 
     
     
       10. An oxygen sensor comprising:
 a housing defining an interior space; 
 a sensing electrode; 
 a reference electrode; 
 a counter electrode, wherein the sensing electrode, the reference electrode and the counter electrode are disposed in a planar arrangement and wherein the reference electrode is disposed between the sensing electrode and the counter electrode; 
 a separator retaining an electrolyte, wherein the electrolyte provides an ionically conductive pathway between each of the sensing electrode, the reference electrode, and the counter electrode within the housing, wherein a shortest path between the sensing electrode and the counter electrode on the ionically conductive pathway exists through the reference electrode; and 
 a chamber within the housing, wherein the chamber contains the sensing electrode, wherein the chamber comprises an opening, and wherein the separator extends into the chamber and substantially fills the opening so that the rate of oxygen diffusion to the sensing electrode is less than a consumption rate of oxygen at the sensing electrode, wherein the opening and the separator are configured to prevent gas from entering the chamber.